This equation computes the energy (in kilowatt hours per year) that can be generated by a small wind turbine.
diam - the diameter of the circle described by the tip of the wind turbine blades
Wind turbine manufacturers routinely give inaccurate or egregiously erroneous information on the potential energy output from wind turbines. Energy production claims are frequently exaggerated.There is evidence that testing in many instances is woefully limited or non-existent. So, we have to rely on physics-based assessment of the power of a blade-based system that is driven by the wind. This equation computes an estimated kWh derived from a wind turbine based purely on its diameter. We will attempt to construct other equations that will do a more detailed analysis of the wind turbine potential.
The energy is calculated is in kWh per year.
This equation was reported to be based on a Weibull wind distribution with a factor of K=2, which is suggested to be a close approximation for inland sites.The Wiebull distribution1 is a continuous probability distribution which is in this case applied to the probability that the wind speed will achieve a mean hourly speed. It gives you a statistical way to propose a reasonable mean wind speed.2
This equation incorporates an overall efficiency factor for the turbine, from wind to electrical grid, of 30% is used. I agree that that is a reasonable, real-world efficiency number.